Fix date range filters on audit event export

The current export has two problems:

- Ending time (i.e. in `created_before`) is set to the start of the day
  (00:00:00), instead of the end of the day (23:59:59). This results in
  a lot of missing events.

- If date range params are not provided, it returns the first 100,000
  events ordered by `created_at`, instead of constraining to only a
  month worth of data like in the search UI.

This change addresses the above issue and, as a result, ensures the
exported content matches with the one presented in the search UI.

ee/app/controllers/admin/audit_log_reports_controller.rb

 # frozen_string_literal: true
 
 class Admin::AuditLogReportsController < Admin::ApplicationController
+  include AuditEvents::DateRange
+
   before_action :validate_audit_log_reports_available!
 
   feature_category :audit_events

ee/spec/controllers/admin/audit_log_reports_controller_spec.rb

@@ -43,10 +43,17 @@ RSpec.describe Admin::AuditLogReportsController do
         end
 
         it 'invokes CSV export service with correct arguments' do
+          expected_params = {
+            entity_type: 'Project',
+            entity_id: '789',
+            created_before: Date.parse('2020-09-01').end_of_day,
+            created_after: '2020-08-01',
+            author_id: '67'
+          }
+
           subject
 
-          expect(AuditEvents::ExportCsvService).to have_received(:new)
-            .with(ActionController::Parameters.new(params).permit!)
+          expect(AuditEvents::ExportCsvService).to have_received(:new).with(expected_params.with_indifferent_access)
         end
 
         it 'returns success status with correct headers', :aggregate_failures do
@@ -74,6 +81,31 @@ RSpec.describe Admin::AuditLogReportsController do
             ["20", "sǝʇʎq ƃuᴉpoɔǝp", ",./;'[]\-= old project", "Project", "¯\\_(ツ)_/¯"]
           ])
         end
+
+        context 'when date range params are not provided' do
+          let(:params) do
+            {
+              entity_type: 'Project',
+              entity_id: '789',
+              author_id: '67'
+            }
+          end
+
+          it 'passes the default date range filter to the CSV export service' do
+            current_time = Time.zone.local(2020, 9, 12, 1, 4, 44)
+            expected_date_range_params = {
+              created_before: current_time.end_of_day,
+              created_after: Date.parse('2020-09-01')
+            }
+
+            travel_to(current_time) do
+              subject
+
+              expect(AuditEvents::ExportCsvService).to have_received(:new)
+                .with(hash_including(expected_date_range_params))
+            end
+          end
+        end
       end
 
       context 'when feature flag is disabled' do